Alcohol and tobacco use during pregnancy have been shown to influence fetal brain development. These exposures have also been associated with intellectual disability, learning difficulties, autism spectrum disorder (ASD) and schizophrenia. Although such associations may be biologically plausible, whether they are causal or not is unclear. As a part of this project we aim to further investigate whether substance use by mothers during pregnancy is causally associated with childhood neurodevelopmental outcomes. To do this we will use a variety of statistical techniques which may improve our understanding. These techniques include comparison of mother and father’s substance use behaviours and the use of genetic methods which help to determine causality. These analyses will be undertaken in several large population based birth cohorts, including ALSPAC, in conjunction with other techniques such as sibling designs. The project will help to expand our understanding of the non-genetic causes of ASD, learning/intellectual disability and psychosis. Our research will provide a stronger evidence base to help future guidelines or policy regarding substance use during pregnancy.